This invention generally relates to an apparatus and method of protecting crops from frost and, in particular, a jet-dispersed, microencapsulated aerosol for protecting crops against frost.
The problem of crop frost protection, for example, protection of orange crops in Florida, has existed in many parts of the world since the beginnings of agriculture. In the past, smoke pots, fires and other cumbersome methods of generating heat have been employed with limited success. More recently, water fogs have been applied to the plants to shield them from the frost. Evaporation of artificial water fogs can be retarded by the application of coatings of long-chain fatty alcohols to the droplets during generation. It has been shown that water fogs coated with cetyl alcohol from a commercial generator have droplet sizes which are inversely proportional to the amount of alcohol used and that, while the coatings affect evaporation rate in droplet size, stabilized water fogs otherwise are spectrally similar to uncoated fogs. In such systems, evaporation was retarded by the condensation of the long-chain alcohol vapor onto water droplets coming from a steam bath; such alcohols, for example, have been used to reduce evaporation from city reservoirs since even a monolayer is effective. But the droplet system has limited utility because the droplets are not uniformly coated. Furthermore, evaporation was retarded only for several seconds, and an effective fog blanket to shield against frost could be maintained only under near-saturation atmospheric conditions. What is needed is an effective way to disperse and stabilize, for minutes to hours, large quantities of water or of other droplets to form a protective frost-resistant crop blanket.
Dispersion of aerosols by injection of fluids or solids into jet engine exhaust gases has been known. But such dispersion techniques have used jet dispersion on a massive scale as a means for disinfecting crops by dispersing insecticides and other materials. Thus, a jet engine is a feasible alternative for dispersing disinfectants as well as fertilizers to crops in the growing season.
There is a need for a system which employs dispersion techniques similar to jet dispersion for distributing microencapsulated droplets of water which have a high latent heat of evaporization and have accessibility in the field without the logistical burden of supplying blocks of cetyl alcohol.